Piezoelectric vibrators have been widely used as oscillators and band-pass filters. For example, as an aspect of a piezoelectric vibrator of the related art, Patent Document 1 describes a surface-mount crystal unit having a structure for hermetically sealing a crystal unit such that the crystal unit will not be exposed to the outside air. The surface-mount crystal unit described in Patent Document 1 includes a substrate onto which a crystal unit is mounted and a lid that hermetically seals the crystal unit with an adhesive interposed therebetween (see in Patent Document 1).
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-197615